A typical example of conventional gas flow measuring devices is a vapor flow measuring device which measures a vapor flow in a high dew point process gas system such as a fuel cell power generation system (see e.g. Japanese Patent No. 2646788 (registered on May 9, 1997) which will be hereinafter referred to as Document 1). A vapor flow measuring device disclosed by Document 1 can precisely measure a vapor flow using a measuring instrument (dew point recorder) which measures a vapor flow (dew point). The vapor flow measuring device disclosed by Document 1 lowers the dew point to be measured, by mixing a known amount of inactive gas into a target gas including vapor, and reducing the partial pressure of the vapor.
In other words, the vapor flow measuring device of Document 1 dilutes a target gas including vapor with a predetermined flow of inactive gas so as to measure the dew point being lowered. This prevents such a problem that, in a high dew point region, a subtle measurement error of the dew point results in a considerable difference of the partial pressure of the vapor. Subsequently, the vapor flow measuring device of Document 1 measures the partial pressure of the vapor from the measured dew point and the pressure at the point of measuring the dew point, so as to measure the vapor flow with reference to the partial pressure of the vapor and the flow of the inactive gas.
However, the vapor flow measuring device of Document 1 is for measuring a vapor flow, thereby not being able to measure gas flows of respective gas components of a mixed gas.
In this regard, there has been no known device which can, by itself, measure gas flows of respective gas components of a mixed gas, and hence gas flows of respective gas components of a mixed gas have typically been measured in the following manner.
First, after measuring a flow of a mixed gas using, for instance, a volume flow meter which can measure any types of gasses, gas concentrations of respective components are measured using any one of a gas chromatography, a mass spectrometer and a spectrophotometer. From the results of these measurements, gas flows of respective gas components of a mixed gas are measured.
That is to say, even if the types of gas components of a mixed gas are known, the volume flow meter cannot measure gas flows of the respective components without being provided with a gas concentration ratio between the components, thereby requiring another analytical instrument such as a gas chromatography and a mass spectrometer. In this manner, since not only a flow of a mixed gas but also a concentration ratio have to be measured, the operation of measuring the flow is complicated and the accuracy of the measurement result is insufficient. Furthermore, the gas chromatography and the mass spectrometer are expensive, large in size, and require a skilled operator.
When an area flow meter or a hot-wire mass flow meter is adopted instead of the volume flow meter, even if the types of gas components of a mixed gas and a gas concentration ratio between the components are known, the gas flow of the respective components cannot be measured. This is because the area flow meter and the hot-wire mass flow meter have to convert the temperature change with gas flowing to a quantity of the flow, for respective components of a mixed gas.